BIOGEOGRAPHY

1. Biogeography is the study of the distribution of biodiversity over space and time. It aims to reveal where organisms live and at what abundance. Biogeography does more than ask Which species? and Where. It also asks Why? and what is sometimes more crucial, Why not? Strictly speaking, biogeography is a branch of biology, but physical geographers have made important contributions, particularly in the study of flora. The classification of vegetation and the preparation of maps of vegetation have been notably advanced by F. Shreve, H.I.Shantz, H.M. Raup and others.

2. The patterns of species distribution at this level can usually be explained through a combination of historical factors such as speciation, extinction, continental drift, glaciation (and associated variations in sea level, river routes, and so on), and river capture, in combination with the area and isolation of landmasses (geographic constraints) and available energy supplies.

3. Modern biogeography often employs the use of Geographic Information Systems (GIS), to understand the factors affecting organism distribution, and to predict future trends in organism distribution. Often mathematical models and GIS are employed to solve ecological problems that have a spatial aspect to them.

4. It is thought that the present-day distribution patterns of plant and animal forms, as reflected in biogeographic regions, are the result of many historical and current causes. These causes include present climatic and geographic conditions, the geologic history of the landmasses and their climates, and the evolution of the taxon (e.g.,genus or species) involved. Investigation have found that rate of dispersal, adaptability to prevailing environmental conditions, and the age of the taxa being studied also have a significant impact on pattern and extent of distribution.

5. The scientific theory of biogeography grows out of the work of Alfred Russel Wallace and other early evolutionary scientists. Wallace studied the distribution of flora and fauna in the Malay Archipelago in the 19^th century. With the exception of Wallace and a few others, prior to the publication of “The Theory of Island Biogeography” by Robert MacArthur and F.O.Wilson in 1967 the field of biogeography was seen as a primarily historical one and as such the field was seen as a purely descriptive one.

6. MacArthur and Wilson changed this perception and showed that the species richness of an area could be predicted in terms of such factors as habitat area, immigration rate and extinction rate. This gave rise to an interest in island biogeography. The application of island biogeography theory to habitat fragments spurred the development of the fields of conservation biology and landscape ecology.

7. Classic biogeography has been expanded by the development of molecular systematics, creating a new discipline known as phylogeography. This development allowed scientists to test theories about the origin and dispersal of populations, such as island endemics. For example, while classic biogeographers were able to speculate about the origins of species in the Hawaiian Islands, phylogeography allows them to test theories of relatedness between these populations and putative source populations in Asia and North America.

8. Paleobiogeography goes one step further to include paleogeographic data and considerations of plate tectonics. Using molecular analyses and corroborated by fossils, it has been possible to demonstrate the perching birds evolved first in the region of Australia or the adjacent Antarctic (which at that time lay somewhat farther north and had a temperate climate). From there they spread to the other Gondwanan continents and Southeast Asia – the part of Laurasia then closest to their origin of dispersal – in the late Paleogene, before achieving a global distribution in the early Neogene. Not knowing the fact that at the time of dispersal, the Indian Ocean was much narrower than it is today, and that South America was closer to the Antarctic, one would be hard pressed to explain the presence of many “ancient” lineages of perching birds in Africa, as well as the many South American distribution of the suboscines.

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